1. Field of the Invention
This invention relates to antibiotics PA-45052 which are represented by the following formula; ##STR1## or H and R.sub.1 denotes CH.sub.3 or H.sub.1), their pharmaceutically acceptable salts, their production, organisms producing them and a growth-stimulating agent containing at least one of them.
2. Prior Art
As antibiotics have recently become to be widely used, the emergence of multiple drug-resistant bacteria, especially methicillin-resistant bacteria provides severe problems. The methicillin-resistant bacteria show resistance not only to methicillin but also to various antibiotics such as aminoglycosides, tetracyclines, cephems, penicillins, carbapenems and macrolides.
It is noticed that glycopeptides, especially vancomycins, show activity against the methicillin-resistant bacteria (Antimicrobial Agent and Chemotherapy, 28, 660-662 (1985)). Vancomycin is a well-known antibiotic (Japanese Patent Publication No. 33-8450) and novel analogs of vancomycin have been discovered (Antimicrobial Agent and Chemotherapy, 28, 660-662 (1985), The Journal of Antibiotics, 37, 446-453 (1984), 38, 1-8 (1985), 38, 51-57 (1985), Japanese Laid-open Patent Nos. 60-139623, 60-199397, 60-231698, 60-237099 etc.). On the other hand, the present inventors found that a strain belonging to the genus Nocardia produces vancomycin antibiotics PA-42867-A and PA-42867-B having a potent antibacterial activity (Japanese Patent Application No. 61-14389) and, in addition, produced its derivatives (Japanese Patent Application No. 61-188865). But the antibiotics PA-45052 of the present invention are vancomycins having completely new structures not coincident to those of the above compounds.
It has been well known that glycopeptide antibiotics such as vancomycins stimulate growth of animals (for example, Japanese Unexamined Patent Publication Nos. 57-129693, 59-213394, 59-213395, 60-199397, 60-231698, 60-237099, 61-122300, 61-251699, 62-126970 and 61-502335; U.S. Pat. Nos. 4,537,770 and 4,558,036; European Patent Publication No. 119575 etc.). However, it has not been known at all that the compounds of this invention have growth-promoting activity. Now, thiopeptin is on the market as growth-stimulating agent.
The problems of infections caused by methicillin-resistant bacteria come to be serious in the clinical field and it is known that glycopeptide antibiotics, especially vancomycin antibiotics have an effectiveness against them. The purpose of this invention is to provide novel vancomycin antibiotics having such an activity as described above and which hence seem to greately contribute to the advancement of medicine.